The present invention relates to a toner, a toner cartridge and a developing device using the same used in an image forming apparatus utilizing an electrophotographic method or an electrostatic recording method, such as a duplicator, a printer and a facsimile.
In the image forming apparatus, such as a duplicator and a printer, an electrophotographic method or an electrostatic recording method based on the Carlson process has been used. In the image forming apparatus using an electrophotographic method or an electrostatic recording method, after an electrostatic latent image formed on a photoreceptor by an optical process is developed by a developing step, the image is transferred to a recording medium, such as recording paper, in a transferring step, and then it is fixed to the recording medium, such as recording paper, in a fixing step generally by heat and pressure, so as to form an image. In order to repeatedly use the photoreceptor for the image formation, a cleaning device for removing a toner remaining on the photoreceptor after completion of transition is arranged.
The developing method used for the development of the electrostatic latent image includes an one-component developing method using only a toner and a two-component developing method using a toner and a carrier. In the developer for the two-component developing method, since the toner is charged by friction through agitating the toner and the carrier, the charging amount by friction of the toner can be controlled to a certain extent by selecting the characteristics of the carrier and the agitation conditions, and therefore it is excellent since the image quality is highly reliable.
In order to produce a toner used in the electrophotographic process, such a production process using a pulverization and classification method is generally employed in that a colorant, a charge controlling agent and a releasing agent are added to a synthetic resin, such as a polyester resin, a styrene-acrylic resin or an epoxy resin, and fused and kneaded therewith to be uniformly dispersed therein. The mixture is then pulverized to have a prescribed particle size, and excess coarse particles and fine particles are removed by a classifying apparatus. It is being demanded to further reduce the particle size of a toner along with the demand of further increasing the image quality. It is also demanded, according to the demand of energy saving, to lower the glass transition point and the softening point of the resin used in the toner for realizing fixing at a lower temperature.
In a color toner used in a full color duplicator and a full color printer, it is necessary that multicolor toners are sufficiently mixed on the fixing step, and the color reproducibility and the transparency of an image for OHP are important. It is generally desired that color toner, in comparison to black toner, is formed with a resin of a sharp melting property having a low molecular weight that can be instantaneously fused and mixed for improving color mixing property.
Wax having a high crystallinity and a relatively high melting point, such as polyethylene and polypropylene, has been used in black toner for obtaining an offset resistance on fixing, but it deteriorates the transparency of an OHP image in the color toner for a full color image. Therefore, the color toner for a full color image does not contain wax, but in order to prevent offset, a surface of a heat fixing roller is formed with silicone rubber or a fluorine resin having a good releasing property to the toner, and a releasing liquid, such as a silicone oil, is further supplied to the surface. Although this method is greatly effective to prevent the offset phenomenon of the toner, there is a problem in that an apparatus is required for supplying an offset preventing liquid to the surface of the heat fixing roller. It is opposite to the trend of decreasing the size and the weight of the apparatus for forming an image, and it sometimes causes another problem in that the offset preventing liquid is heated and evaporated to form an offensive odor and contaminates the inside of the apparatus.
According to the circumstances, a full color toner is greatly demanded in that the multicolor toners are sufficiently mixed to ensure the offset resistance in the fixing step, the color reproducibility and the transparency of an OHP image even though an offset preventing liquid is not used but wax is used. Thus, such a toner having a small particle size is being demanded that contains wax having a low melting point by the pulverization and classification method, and is formed with a resin of a sharp melting property and a colorant.
The toner is forcedly agitated and transported from a toner cartridge to develop an electrostatic latent image on a photoreceptor, and after transferring the resulting toner image to a recording medium, the toner image is fixed to the recording medium. In this process, it is necessary to use an agitating and transporting member, such as an agitator and an auger, for forcedly agitating and transporting the toner.
However, in the case where the toner mentioned in the foregoing is subjected to a repeated agitation and transportation test on the toner cartridge having the agitating and transporting member, the toner is liable to be deformed in comparison to the conventional black and white toner and the color toner containing no wax, and the toner contains a relatively large amount of toner particles having a small diameter, which have relatively large attaching property. Thus, the toner receives mechanical stress by friction of the toner and a contacting part, such as an inner wall, and accumulation of the toner on the concave parts, whereby aggregates of the toner are formed. It is also considered that the part where the wax is exposed on the surface of the toner is the cause of the formation of aggregates of the toner. When the aggregates of the toner are developed, a problem is caused by forming defects on an image.
The invention has been developed to solve the problems associated with the conventional techniques and to provide a toner, a toner cartridge and a developing apparatus using the same realizing stable agitation and transportation of a toner, by which an excellent image having no defect can be obtained for a long period of time.
The invention relates to, as a first aspect, a toner cartridge comprising a toner and a toner agitating and transporting member for supplying the toner under agitation and transportation from inside the toner cartridge, the toner having a binder resin, a colorant and a wax, the wax is in an amount of from 1 to 15% by weight of the toner and the toner having a mean particle diameter of from 3to 10 xcexcm, and the toner agitating and transporting member being arranged as rotatably inside the toner cartridge to form a distance of from 0.5 to 3.0 mm between the member and an inner wall of a main body of the toner cartridge.
In the first aspect of the invention, it is preferred that the toner further contains inorganic fine particles in an amount of from 1 to 10% by weight.
The invention also relates to, as a second aspect, a developing device comprising a toner and a toner agitating and transporting member and a developer holding member for developing an electrostatic latent image by the toner on the surface of the developer holding member, the toner having a binder resin, a colorant and a wax, the wax is in an amount of from 3 to 10% by weight and the toner having a mean particle diameter of from 3 to 10 xcexcm, the toner agitating and transporting member transporting the toner to a developer holding member, and the toner agitating and transporting member being arranged as rotatably inside the main body of the developing device to form a distance of from 0.5 to 3.0 mm between the member and an inner wall of the developing device.
In the second aspect of the invention, it is preferred that the toner further contains inorganic fine particles in an amount of from 1 to 10% by weight.
The invention also relates to a process for forming an image employing the developing device.